This is an industry sponsored (DuPont Merk) multi-centered, randomized, double-blind dose escalating study to evaluate the safety, tolerability, pharmacokenetics (PK) and pharmacodynamics (PD) of DMP 777 in adults with cystic fibrosis. Objectives are to assess the magnitude of extracellular human neutrophil elastase inhibitory activity in BAL fluid, to correlate this effect with PK and PD parameters and to evaluate the safety of DMP 777. Secondary objectives are to correlate change from baseline with quality of life measures and biologic indicies.